The present invention relates to a method of simultaneously producing a number of cigarette rods.
In cigarette manufacturing machines, and as described in U.S. Pat. No. 4,336,812, at least two parallel, side by side strips of paper are fed on to respective conveyor belts, the transportation branches of which extend over a forming bed and through a loading station where a central portion of each strip is fed with a respective continuous layer of shredded tobacco. Downstream from the loading station, the transportation branches of the conveyor belts engage respective variable-section grooves formed along a forming beam fitted to the forming bed, and are deformed transversely by the grooves to gradually wind the respective strips about the respective layers of tobacco to form respective tubular wrappings. Each of the wrappings presents a respective longitudinal lateral appendix, the inner surface of which is gummed by a respective gumming device and then brought into contact with the outer surface of the tubular wrapping to form a respective continuous cigarette rod.
As described in U.S. Pat. No. 4,336,812 referred to above, to simplify assembly and maintenance of the gumming devices, these are located on opposite sides of the forming beam. Such an arrangement, however, in addition to seriously complicating any intervention on the forming bed on the part of the operator, and the assembly of removable safety covers on the outward-facing part of the forming bed, also limits the location and orientation of said inner surfaces and hence the structure of the respective grooves.
To overcome this drawback, the gumming devices are therefore known to be located upstream from the loading station. Even this solution, however, is not without drawbacks, in that, on reaching the loading station, each paper strip presents a lateral portion gummed on the side facing the respective layer of tobacco, so that any stray particles of tobacco from the layer may adhere to the gummed portion of the strip, thus resulting in the formation of defective cigarettes.